Forum Discussion

lawrosa's avatar
lawrosa
Explorer
Mar 14, 2018

Air bags increase tongue or pin weight??? Interesting!!

Came across this video.. It seems air bags increase TW when adjusted for a level ride.

I never would of assumed this..

I would think the same for the 5th wheel guys. Its interesting none of the airbag guys stated this in their scale measurements.

At least I have not read about it. Maybe its a big secret.

Would that mean preferred would be add a leafs, of bump stop for the overloads would do a better job?

Im trying to figure in my head why this is so..

https://www.youtube.com/watch?v=XBZu39pQ8Gg
  • Chum_lee's avatar
    Chum_lee
    Explorer
    Mar 17, 2018
    mike-s wrote:
    red31 wrote:
    lawrosa wrote:



    For anyone who has a hard time understanding why the airbags increase the rear (axle) weight - they push down on the axle in order to push the frame up.



    I understand why axle loads change using the load equalizing bar vs. the air bags but I'm having a hard time understanding your analogy. So, . . . are you saying that I weigh more standing up than when I'm sitting down? Please explain.

    Chum lee
  • mike-s's avatar
    mike-s
    Explorer
    Mar 14, 2018
    red31 wrote:
    lawrosa wrote:

    Hey its winter in NJ. I need something to do...


    re watch and add up the weights for each scenario.

    Baseline 11,585 lbs
    Sag 11,695 lbs - 110 lb increased mass created out of thin air
    leveled 11,715 lbs - more mass created
    WDH 11,725 lbs - 10 lbs of spring bars

    where o where did they measure TW, and why not compare to a ball a couple inches closer to the truck. This much effort and sloppy results.
    They measured tongue weight toward the beginning, and in the comments said they "used a simple hydraulic scale to get the trailer's tongue weight", not one of the 1% accurate digital ones. So, that scale was apparently ~120 lbs. low. Considering that (and the weight of the bars), the rest of the weights were within a +-15 lb range, well within the scale's accuracy and resolution (which looks to be 5 lbs.).

    For anyone who has a hard time understanding why the airbags increase the rear weight - they push down on the axle in order to push the frame up.
  • red31's avatar
    red31
    Explorer
    Mar 14, 2018
    lawrosa wrote:

    Hey its winter in NJ. I need something to do...


    re watch and add up the weights for each scenario.

    Baseline 11,585 lbs
    Sag 11,695 lbs - 110 lb increased mass created out of thin air
    leveled 11,715 lbs - more mass created
    WDH 11,725 lbs - 10 lbs of spring bars

    where o where did they measure TW, and why not compare to a ball a couple inches closer to the truck. This much effort and sloppy results.
  • Chum_lee's avatar
    Chum_lee
    Explorer
    Mar 14, 2018
    wa8yxm wrote:
    The Max Combined Vehicle Weight is not changed by addition of air bags.
    But the weight distribution may be. so for some vehicles with more of the weight moved to the FRONT you can tow more. this is what a load equalizing hitch does.

    A air bag just lifts the rear. exceeding rear axle ratings can be... bad.


    IMO, this is correct. Towing (weight distribution) with a ball type trailer hitch vs. a 5th wheel hitch is not the same statically or dynamically. With a 5th wheel type tow hitch, the trailer tongue weight is applied to the tow vehicle as close to directly above the rear axle as possible. (this is adjustable) That minimizes the moment that the 5th wheel tongue weight imparts to the frame of the tow vehicle. The tongue weight of a ball type trailer hitch loads the tow vehicle well BEHIND the rear axle. The moment imparted into the frame of the tow vehicle reduces weight on the front axle and adds it to the rear axle, possibly, under some conditions, overloading it. The weight distribution bar (load equalizing bar) reduces the vertical angular flexibility of the ball and socket type trailer hitch. Air bags do nothing to change the flexibility of a ball and socket type trailer hitch so the final weight distribution seeks the path of least resistance.

    Chum lee
  • wa8yxm's avatar
    wa8yxm
    Explorer III
    Mar 14, 2018
    The Max Combined Vehicle Weight is not changed by addition of air bags.
    But the weight distribution may be. so for some vehicles with more of the weight moved to the FRONT you can tow more. this is what a load equalizing hitch does.

    A air bag just lifts the rear. exceeding rear axle ratings can be... bad.
  • valhalla360's avatar
    valhalla360
    Navigator
    Mar 14, 2018
    Assuming we are talking about a 5th wheel or a simple ball and only an inch or two of sag removed...no, there should be no measurable difference. There simply isn't a mechanism to change the loading on the rear axle (theoretically, centers of gravity shift but so little that you won't be able to measure it reliably).

    With a weight distributing hitch...it depends:
    - If you set up the hitch, leave everything else the same and then pump up the air bags the torsion bars will be put under greater strain. This will increase the hitch weight and increase the rear axle loading (it will also increase the front axle but by a smaller amount).
    - If you pump up the airbags and then adjust the torsion bars to provide roughly the same weight distribution, there should be no significant difference (trick is to know how much strain you are putting the torsion bars under)

    If you have a goal of increasing the rear axle load, simply shorten up the chains on the torsion bars a couple of links and you will achieve the same thing.
  • lawrosa's avatar
    lawrosa
    Explorer
    Mar 14, 2018
    Well I did the calculation in towing planner.

    With the air bags at 4.5 psi and the trailer on the TW of that trailer is 895 lbs. Not sure where they got the 1000 lb TW from

    Its also 18.3%.

    They are slightly off on their trailer weight. I think. Shoes here trailer weighs 4895 So they are 100 lbs lower...


    http://towingplanner.com/ActualWeights/TravelTrailerCatScales/?w2sa=3675&w2da=4020&w2ta=4000&w3sa=4005&w3da=2795&a=2

    Now at 55psi in the bags the TW according to towing planner is 1005lbs

    And @ 20.4%


    http://towingplanner.com/ActualWeights/TravelTrailerCatScales/?w2sa=3650&w2da=4155&w2ta=3910&w3sa=4005&w3da=2795&a=2

    So looks like its accurate just a slight off # on thier tongue weight..


    And inputting the WD here is irrelevant. They restored the front axle close to original ride height. This is back with the original no/wd and with wd..

    http://towingplanner.com/ActualWeights/TravelTrailerCatScales/?w1sa=3925&w1da=3650&w1ta=4150&w2sa=3675&w2da=4020&w2ta=4000&w3sa=4005&w3da=2795&a=2


    So there you have it.... Get a 5th wheel thats too heavy and you have sag???? Air bags may level the ride but may make you go over your axle ratings if your close in that respect...

    Interesting to say the least.

    Ha ha ha... Im not stirring the pot, but just saying is all..

    Hey its winter in NJ. I need something to do...


    I know I know.... Its only 110lb increase... .... he he...:S

    They did some smoke and mirrors with the #'s at the end of that video I would assume....

    Moralof the story ... Do the math...

    At least I think my math is right..

    Hey they are good sales men...
  • lawrosa's avatar
    lawrosa
    Explorer
    Mar 14, 2018
    bid_time wrote:
    Where you been? People been advocating for loading up to the RAWR for years.


    I guess i've been living in a cave!!!!!
  • DrewE's avatar
    DrewE
    Explorer II
    Mar 14, 2018
    Geometrically, I think the tongue weight should be slightly greater if the tongue is low assuming the center of gravity of the trailer is higher than the pivot point of its suspension, if there's no weight distributing hitch to mess with things. With a weight distributing hitch, I could see how the hitch geometry could easily come into play to alter how much weight gets distributed as its angle from horizontal changes.

    If an air suspension setup weighs more than an extra leaf or helper spring, then it would load the rear axle more by that additional weight, trailer or no trailer. That part's kind of in the "duh" department. Putting a cinder block in the truck bed over the rear axle would likewise add to its weight in the same manner....
  • Lwiddis's avatar
    Lwiddis
    Explorer II
    Mar 14, 2018
    Doesn’t anything added to the TV subtract from the TV payload?

About Technical Issues

Having RV issues? Connect with others who have been in your shoes.24,228 PostsLatest Activity: Apr 04, 2025